IL21 and systemic lupus erythematosus: Moreover, Tfh cells play a significant role in the occurrence of SLE, so we can conclude that the positive feedback loop regulation of BCL-6-IL-21 may promote Tfh cell differentiation and function in CD4 + T cells in lupus and prompt the interaction of T cells and B cells, resulting in overproduction of self-reactive antibodies and thus promoting the occurrence and development of SLE.